1. Field of the Invention
This invention relates to lubricants, and more particularly to lubricants based on silicone waxes to produce a relatively dry lubricant for mechanical devices that are typically exposed to dirty or dusty environments.
2. Related Art
Lubricants are used to coat mechanical surfaces with a thin film to reduce friction, heat and wear between solid surfaces. In addition to reducing friction, lubricants, particularly wax-based lubricants, can protect mechanical surfaces by sealing them from exposure to water and particulate matter that can corrode or damage the surface, particularly metal surfaces.
Silicones refer to organosilicon oxide polymers in which the structural unit is typically --R.sub.2 Si--O--, where R is an organic radical (e.g., methyl, phenyl). Silicones can be fluids, resins, elastomers or a powder. The physical properties of silicone polymers depend on the size and type of R radical, the R:Si ratio, and the polymeric molecular configuration (e.g., linear, cyclic or combination thereof, and degree of crosslinking). These semiorganic polymers are generally heat stable and water repellent, and have been used as in lubricants, hydraulic oils, adhesives, synthetic rubbers and other elastomers, mold releasing compositions, paints and enamels, water repellents, cosmetics and pharmaceuticals. The chemistry and manufacturing of silicones is well known (e.g., as reviewed in Encyclopedia of Polymer Science and Technology, vol. 12, pp. 464-569, Interscience, New York, 1970).
Some silicone-containing lubricants and their uses are described, for example, in U.S. Pat. Nos. 5,338,312, 5,393,442, 4,731,189 and 4,269,739. Polymer-containing lubricants have been described in U.S. Pat. No. 1,935,588. Other types of lubricants and additives for lubricants known in the art, as described in U.S. Pat. Nos. 3,692,678 and 4,260,500. Lubricants that include soaps are disclosed in U.S. Pat. Nos. 1,920,202, 1,953,904, 2,386,553, 2,391,113, 2,393,797, 2,418,075 and 2,419,713.
Lubricants that remain relatively liquid after application to a mechanism are undesirable for certain environments and machinery. For example, mechanical devices that are exposed to dust or dirt will collect and retain contaminants in a liquid lubricant, eventually causing abrasion and limiting performance of the mechanism. Liquid lubricants also expose the user or products to soiling (e.g., fabrics produced by textile-manufacturing machines). Liquid or semi-liquid lubricants are inappropriate for many types of mechanisms that move at high speeds (e.g., drills, saw blades or chains) because the lubricant will be thrown off of the device by centrifugal or vibrational force on the mechanism. For such uses, dry lubricants or solid lubricants applied to hot metal are often preferred.
Relatively dry lubricants and their uses for coating mechanical devices are known. For example, U.S. Pat. No. 1,694,148 discloses a lubricant suitable for dry lubrication of textile machines. Liquid lubricants that contain salts of fatty acids and become relatively dry after application to bicycle chains are disclosed in U.S. Pat. No. 5,472,625 and allowed U.S. patent application Ser. No. 08/566,680. Solid lubricants that contain waxes with high melting points (e.g., about 71-74.degree. C.) to confer hardness are described in U.S. Pat. No. 2,444,357.
Sprocket and chain mechanisms such as those used on bicycles and motorcycles are complex structures that require lubrication, that are typically used in wet and/or dusty environments. Moreover, these mechanisms are often exposed to relatively high temperatures during use. Non-tacky (i.e., dry or low viscosity) lubricants are preferred for use on bicycle chains or similar mechanisms to prevent accumulation of dust and dirt, and, thus, to prevent abrasion. Although greases accumulate dirt, they are often used to provide even power transmission because of their lubricating capacity on rollers of the chain, which are subject to unbalanced and relatively high pressure on the cross axis, and on sprocket teeth and the outside surface of the rollers, which are subject to shearing contact.
Paraffin-based soap-containing lubricants, such as those disclosed in U.S. Pat. No. 5,472,625 and allowed U.S. patent application Ser. No. 08/566,680 have achieved considerable commercial success, particularly among sports bicyclists (e.g., WHITE LIGHTNING.RTM., Leisure Innovations, Morro Bay, Calif.). These lubricants have the advantage of keeping chains clean by sloughing dirt off of the chain, along with a portion of the lubricant. Paraffin-based lubricants must, therefore, by reapplied relatively frequently (e.g., about every 200 miles for bicycle use).
For high performance or professional bicyclists, however, paraffin-based lubricants may not provide the even power transmission needed, for example, during competitive racing events. Because such events often take place in wet and/or dusty conditions, there is a need for a lubricant that will deliver high-performance lubrication with even power transmission under wet and dirty conditions.
Smooth, high-performance lubrication is also needed for power tools used in dusty environments, such as drills and saws used for fabricating wood, plastic and metal objects. Thus, there is a need for a high-performance dry lubricant suitable for use with metal, wood and plastic surfaces. Similarly, there is a need for a dry lubricant for application to powered or manually driven household appliances, office and gardening equipment. Additionally, there is a need for a lubricant for mechanisms that operate in hot, dusty or wet environments, such as computer printers, paper shredders and fishing reels, as well as near combustion engines found on motorcycles, powered lawn equipment, farm equipment, forklifts, and other industrial or construction equipment.